Stamping is a molding process in which a press and a die are used to apply an external force to plates, strips, tubes and profiles, etc., to produce plastic deformation or separation, so as to obtain a workpiece of the desired shape and size (stamped part). Stamping and forging are the same plastic processing (or pressure processing), collectively referred to as forging and pressing. The blanks for stamping are mainly hot-rolled and cold-rolled steel plates and strips. The world's steel, 60 to 70% of the plate, most of which are stamped into finished products. Automobile body, chassis, fuel tanks, radiator panels, boiler ladle, container shells, motors, electrical appliances, iron core silicon steel sheet, etc. are stamping process. Instruments and meters, household appliances, pedal cars, office machinery, household utensils and other products, there are also a large number of stamping parts.
Stamping is the power of conventional or special stamping equipment, so that the sheet in the mold directly by the deformation force and deformation, so as to obtain a certain shape, size and performance of the product parts of the production technology. Sheet, mold and equipment is the three elements of stamping. According to the stamping processing temperature is divided into hot stamping and cold stamping. The former is suitable for high deformation resistance, poor plasticity of the sheet processing; the latter is carried out at room temperature, is a common stamping method of thin plate. It is one of the main methods of metal plasticity processing (or pressure processing), and is also subordinate to the material molding engineering technology.
The mold used for stamping is called a stamping die, or die for short. The die is a special tool for batch processing of materials (metallic or non-metallic) into the required punched parts. Stamping die in stamping is crucial, no meet the requirements of the stamping die, batch stamping production is difficult to carry out; there is no advanced die, advanced stamping process can not be realized. Stamping process and molds, stamping equipment and stamping materials constitute the three elements of stamping processing, only they are combined with each other in order to come up with stamped parts.
Basic introduction Chinese name ：冲压 Foreign name ：sheet metal forming；stamping Note ：chòng yā Full name ： cold stamping Applicable fields ：automotive production Processing characteristics，Problems，Solutions，Process classification，Separation process，Forming process，Materials，Molds,Die，Specialized equipments，Lubrication，Safety production, Processing characteristics Stamping parts and castings, Compared with castings and forgings, stamped parts are characterized by thinness, uniformity, lightness and strength. Stamping can produce workpieces with reinforcement, ribs, undulations or flanges, which are difficult to be manufactured by other methods, in order to improve their rigidity. Due to the use of precision molds, the accuracy of the workpiece can reach the micron level, and high repeatability, consistent specifications, can be stamped out of the hole nests, tabs and so on. Cold stamped parts are generally no longer cut and processed, or only a small amount of cutting. Hot stamped parts precision and surface condition is lower than cold stamped parts, but still better than castings, forgings, less cutting. Stamping stamping is a highly efficient production method, the use of composite molds, especially multi-position progressive die, in a press (single-position or multi-position) on the completion of a number of stamping processes, to achieve the full-automatic production from the strip to uncoil, leveling, punching to the forming, finishing. High production efficiency, good labor conditions, low production costs, generally can produce hundreds of pieces per minute. Compared with other methods of machining and plastic processing, press processing has many unique advantages in both technology and economy. The main performance is as follows. stamping tee (1) stamping processing of high production efficiency, and easy to operate, easy to realize mechanization and automation. This is because the stamping is relying on the stamping die and stamping equipment to complete the process, the number of ordinary press strokes per minute up to dozens of times, high-speed pressure per minute up to hundreds or even thousands of times, and each stamping stroke may be a punch. (2) Stamping due to the mold to ensure the size and shape of the stamped parts of the precision, and generally do not damage the surface quality of the stamped parts, and mold life is generally longer, so the quality of the stamping is stable, interchangeable, with the "one and the same" characteristics. (3) Stamping can be processed to produce parts with larger size range and more complicated shapes, such as the second hand of a watch, the longitudinal beam of an automobile, cover parts, etc. Together with the cold deformation and hardening effect of the material during stamping, the strength and stiffness of stamping are higher. (4) Stamping generally does not generate chips and debris, less material consumption, and does not require other heating equipment, so it is a kind of material-saving, energy-saving processing methods, the cost of stamped parts is lower. Because stamping has such superiority, stamping processing is widely used in various fields of national economy. For example, stamping is used in aerospace, aviation, military, machinery, agricultural machinery, electronics, information, railway, post and telecommunications, transportation, chemical industry, medical equipment, daily appliances and light industry. Not only the whole industry uses it, but also everyone is directly related to stamping products. Like airplanes, trains, automobiles, tractors, there are many large, medium and small stamping parts. Small car body, frame and rim and other parts are stamping processed out. According to relevant survey statistics, bicycle, sewing machine, watch, 80% of the stamping parts; TV, recorders, video cameras, 90% of the stamping parts; and food metal can shells, steel pots and pans stove, enameled pots and bowls and stainless steel cutlery, all of which are the use of molds of the stamping process products; even the computer's hard body is also the lack of stamping parts. Problems 1, mold problems Stamping processing molds generally have special features, sometimes a complex part requires several sets of molds in order to be processed and shaped, and high precision mold manufacturing, high technical requirements, is a technology-intensive products. Therefore, only in the case of larger production batches of stamped parts, the advantages of stamping can be fully realized, so as to obtain better economic benefits. 2, safety issues stamping processing also has some problems and shortcomings. Mainly in the stamping processing of noise and vibration produced by the two public nuisance, and the operator's safety accidents occur from time to time. However, these problems are not entirely due to the stamping process and mold itself, but mainly due to the traditional stamping equipment and backward manual operation. With the progress of science and technology, especially the development of computer technology, with the progress of mechatronics technology, these problems will be solved as soon as possible and perfect. 3, high-strength steel stamping Today's high-strength steel, ultra-high-strength steel is very good to achieve lightweight vehicles, improve the vehicle's collision strength and safety performance, so it has become an important development direction of automotive steel. However, with the increase in plate strength, the traditional cold stamping process is prone to rupture during the molding process, which cannot meet the processing requirements of high-strength steel plate. In the case of not being able to meet the molding conditions, the international community is now gradually studying the hot stamping and forming technology of ultra-high-strength steel plates. The technology is a combination of forming, heat transfer and tissue phase change of a new process, mainly the use of high temperature austenite state, the plasticity of the plate increases, the yield strength decreases the characteristics of the process of forming through the mold. However, hot forming requires in-depth research on process conditions, metal phase change, and CAE analysis technology, which is currently monopolized by foreign manufacturers, and the domestic development is slow. Solution In the past, when producing deep-drawing or heavy-drawing workpieces, it was thought that pressure-resistant (EP) lubricant was the best choice to protect the molds. Sulfur and chlorine EP additives have been mixed into pure oil to improve mold life for a long time. But with the advent of new metals - high-strength steels - and stringent environmental requirements, the value of EP oil-based lubricants has diminished or even lost its market. Molding high strength steels at high temperatures, EP oil-based lubricants lose their ability to provide a physical mold protection diaphragm in extreme temperature applications. Instead, extreme temperature IRMCO high-solids polymer lubricants provide the necessary protection. As the metal is deformed in the stamping die and the temperature continues to rise, the EP oil-based lubricants all thin out, and in some cases reach flash point or burn (smoke.) IRMCO water-based stamping lubricants generally begin to spray on at a much lower consistency. As the temperature rises during the molding process, it becomes thicker and tougher. Polymer extreme temperature lubricants are actually "heat-seeking" and stick to the metal, forming a barrier that reduces friction. This protective barrier controls friction and metal flow by allowing the part to stretch without cracking or bonding during the most demanding part molding. This effectively protects the die, extends die life and improves the strength of the stamping. Process Classification Stamping is mainly categorized by process and can be divided into two main categories: separation process and forming process. Separation process, also known as blanking, is aimed at separating the stamped parts from the sheet along a certain contour line, and at the same time ensuring the quality of the separated section. The purpose of the forming process is to make the sheet plastic deformation without breaking the blank conditions, made of the required shape and size of the workpiece. In actual production, it is often a variety of processes combined for a workpiece. Stamping, bending, shearing, stretching, expanding, spinning, straightening are some of the main stamping process. Stamping Separation process (blanking) is the use of molds to separate the material of a basic stamping process, which can be made directly into flat parts or other stamping processes such as bending, deep drawing, forming, etc. to prepare blanks, but also in the stamping has been shaped on the notch, trimming and so on. Stamping is widely used in automobile, household electrical appliances, electronics, instrumentation, machinery, railway, communications, chemical industry, light industry, textile and aerospace and other industrial sectors. Stamping process accounts for about 50% to 60% of the entire stamping process. Forming process bending : metal plate, pipe fittings and profiles into a certain angle, curvature and shape of the plastic molding method. Bending is one of the main processes widely used in the production of stamped parts. Bending of metal materials is essentially an elastic-plastic deformation process, after unloading, the workpiece will produce the direction of elastic recovery deformation, called springback. Springback affects the accuracy of the workpiece, is the bending process must consider the technical key. deep drawing : deep drawing, also known as stretching or calendering, is the use of molds to make blanks obtained after punching into open hollow parts of the stamping process. With deep drawing process can be made into cylindrical, stepped, conical, spherical, box-shaped and other irregularly shaped thin-walled parts. If with other stamping forming process, can also make the shape of extremely complex parts. In stamping production, there are many types of deep drawing parts. Because of its different geometric features, the location of the deformation zone, the nature of the deformation, the distribution of deformation and the stress state of each part of the billet and the distribution of the law has a considerable, and even essential differences. So the process parameters, the number of processes and the order of the determination of the method and mold design principles and methods are not the same. A variety of deep-drawing parts according to the characteristics of deformation mechanics can be divided into straight wall rotary body (cylindrical parts), straight wall non-rotary body (box-shaped body), curved surface rotary body (curved shape parts) and curved surface non-rotary body and other four types. Pull Form is through the pull form mold on the plate to exert tensile force, so that the plate produces uneven tensile stress and tensile strain, and then the plate and the pull form mold fit surface gradually expand, until and pull the shape of the model surface completely fit. The applicable object of pulling shape is mainly to manufacture double curvature skin with certain plasticity of the material, large surface area, gentle and smooth curvature changes, and high quality requirements (accurate shape, smooth streamline, stable quality). Pull shape due to the process equipment and equipment used is relatively simple, so the cost is lower, more flexible; but the material utilization and productivity is low. Spinning is a metal rotary machining process. In the process, the blank with the rotary die active rotation or rotary head around the blank and rotary die active rotation, rotary head relative to the core mold and blank for feed movement, so that the blank to produce continuous local deformation and obtain the required hollow rotary body parts. Shaping is the use of the established shape of the abrasive tool to the shape of the product for the second time. This is mainly done in the form of flats and feet. It is used when the elasticity of some materials makes it impossible to guarantee the quality of the primary molding. Expansion is the use of molds to make the sheet stretching thin local surface area to obtain parts of the processing method. Commonly used are undulation molding, cylindrical (or tubular) blanks of the expansion and flat blanks tensile molding. Expansion can be realized using different methods, such as rigid mold expansion, rubber expansion and hydraulic expansion. flanging is along the curve or straight line will be thin plate blank edge or blank on the prefabricated holes in the edge of the narrow band of material in the region of the plastic processing method of bending into vertical edges. Flanging is mainly used to strengthen the edges of the parts, remove the cut edges as well as made in the parts with other parts assembly, connecting parts or with complex special shape, reasonable space of the three-dimensional parts, while improving the stiffness of the parts. It can also be used as a means of controlling rupture or crease when forming large sheet metal. So in the automobile, aviation, aerospace, electronics and household appliances and other industrial sectors to get a very wide set of use. Shrinkage is a stamping method that reduces the diameter of the open end of a flangeless hollow part or tube blank that has been stretched. Shrinking before and after the end of the workpiece diameter change should not be too large, otherwise the end of the material will be compression deformation due to intense wrinkles. Therefore, necking from a larger diameter to a very small diameter often requires multiple necking. Material The surface and internal properties of the sheet material used for stamping have a great influence on the quality of the finished stamped product. The requirements for stamping materials are: ① Precise and uniform thickness. Stamping mold precision, small gap, sheet thickness will increase the deformation force, and cause jamming, and even the concave mold expansion; sheet is too thin will affect the quality of finished products, and even cracking in the deep drawing. stamping raw materials ② surface finish, no spots, no scars, no abrasions, no surface cracks. All surface defects will remain on the surface of the finished workpiece, crack defects in the bending, deep drawing, molding and other processes may be extended to the deep and wide, resulting in scrap. (iii) Uniform yield strength with no apparent directionality. Anisotropy (see plastic deformation of the sheet in the deep drawing, flanging, expansion and other stamping process, due to the appearance of the yielding of each direction is sequential, the amount of plastic deformation is inconsistent, will cause uneven deformation, so that the molding inaccurate and resulting in substandard or scrap. ④High uniform elongation. In the tensile test, the elongation of the specimen before the beginning of the phenomenon of thin neck is called uniform elongation. In deep drawing, the deformation of any area of the sheet must not exceed the uniform extension range of the material, otherwise uneven deformation will occur. ⑤ Low yield-to-strength ratio. The ratio of the yield limit to the strength limit of a material is called the yield-to-intensity ratio. A low yield-strength ratio not only reduces the deformation resistance, but also reduces the tendency to wrinkle during deep drawing, reduces the amount of springback after bending, and improves the accuracy of bent parts. (6) low work hardening. Cold deformation after the emergence of work hardening will increase the deformation resistance of the material, making it difficult to continue to deform, so the general use of low hardening index of the plate. However, high hardening index of the material's plastic deformation stability (i.e., plastic deformation is more uniform), not easy to appear localized cracking. In actual production, commonly used with the stamping process approximate process test, such as deep drawing performance test, expansion performance test test test material stamping performance, to ensure the quality of the finished product and a high pass rate. Mold The precision and structure of the mold directly affect the forming and precision of the stamped parts. The mold manufacturing cost and life are important factors affecting the cost and quality of stamped parts. Tooling design and manufacturing takes more time, which extends the production lead time for new stamped parts. Mold base, mold frame, guide the standardization and development of simple mold (for small batch production), composite mold, multi-position progressive die (for mass production), as well as the development of rapid die change device, can reduce the workload of stamping production preparation and shorten the preparation time, can be applied to mass production of advanced stamping technology reasonably for small batch production of many varieties of sets. Stamping Specialized equipment In addition to the thick plate with hydraulic press forming, generally use mechanical presses. Modern high-speed multi-station mechanical press as the center, configure the uncoiling, leveling, finished product collection, transportation and other machinery, as well as mold library and quick mold change device, and the use of computer program control, can be composed of high productivity automatic stamping production line. Press lubrication General workpiece in the stamping process, due to the stamping process, especially in the cold forging stamping process, the temperature will rise quickly, must be added to the lubricant lubrication, if you do not use the lubrication and direct stamping, in addition to the workpiece finish is affected by the mold life will be shortened, while the precision is reduced, for this reason, the mold aspects of the improvement will be a large amount of investment costs. It is for this reason, so in the cold forging stamping must be stamping lubrication. Safe production in the production of dozens or hundreds of stamping parts per minute, in a short period of time to complete the feeding, stamping, out of the piece, row of waste and other processes, often occurring personal, equipment and quality accidents. Therefore, safe production in stamping is a very important issue. The safety measures for stamping are: ① Realize mechanization and automation of feeding and discharging. ② Set up mechanical guards to prevent injury to hands. Set mold guards, automatic withdrawal devices and hand tools in and out of the material. ③Set up electrical protection and power-off devices. Setting photoelectric or air curtain protection switch, two-handed or multi-handed tandem start switch, anti-misoperation device. ④Improve the clutch and brake structure, the crankshaft, connecting rod, and punch of the press can be stopped in its original position immediately after the danger signal is issued.